Since first introduced in the latter part of the 1800's as “electromagnets” and more commonly since the 1930's to present as “permanent magnets”, magnetic separators have been used to improve product quality of non-ferrous materials and to protect process machinery from damage caused by unwanted metals (metal contaminants) being commingled with non-ferrous materials during the manufacturing and/or product refinement process. Unwanted or commingled ferrous metals and non-ferrous materials can also pose a safety hazard where combustible materials such as wood, grains or other similar materials are being handled. For these reasons it is imperative that a magnetic separator is used to remove unwanted metal contaminants.
Maintaining and improving non-ferrous materials product quality use a variety of methods. Known methods can be as informal as simply removing captured metal contaminants from a magnetic separator when found during periodic or random manual inspections of the magnetic separator, to highly structured and documented quality control processes adopted by the user as part of their materials manufacturing process. These more structured methods include but are not limited to Hazard Analysis Critical Control Points (HACCP), Total Quality Manufacturing (TQM), Good Manufacturing Processes (GMP), to name a few. These more formal methods directed towards product quality are internationally recognized and are accepted processes by global governmental agencies such as the United States Food and Drug Administration (FDA), Food Safety Modernization Act (FSMA), Global Food Safety Initiative (GFSI), International Organization for Standardization (ISO), British Retail Consortium (BRC), Safe Quality Food (SQF), to name a few. To ensure these formal quality standards are constantly maintained in production facilities, they are often monitored not only by internal quality control staff, but include third party outside auditing and certification.
Also, since the development of permanent magnets, the electromagnet has had a somewhat limited role as a viable solution when selecting a magnetic separator. One exception of where electromagnets are desired over permanent magnets is when very large magnets are used to project effective magnetic fields at great distances from the magnetic separator. Commonly, these applications are found in minerals mining and recycling materials process, to name a few. Otherwise, permanent magnets are often the preferred choice, due to a few primary reasons.
First, an electromagnet is typically much larger than a comparable permanent magnet for a specific application. Because of its superior magnetic strength, a permanent magnet is typically more effective in capturing unwanted metal contaminants when compared to a similar sized electromagnet. Because the permanent magnet does not require electricity or a controller to operate, it is often less expensive to manufacture and more reliable than an electromagnet. Since the inception of newer more powerful ferrite and rare earth permanent magnets, permanent magnets are capable of effectively capturing metals that electromagnets may not be able to capture.
When magnetic separators are used in a process as discussed herein, one important purpose of the magnetic separator is to remove metals from non-ferrous materials that are being processed. This is accomplished by placing magnets of a magnetic separator in proximity to the materials being processed so that any metal contaminants are captured and held by the magnets as the materials being processed either make intimate contact with the magnets' working surface, or pass through the magnets' working air gap. Once the metals have been captured by the magnets, and before oncoming non-ferrous material stream flows are able to wipe off or otherwise re-commingle the metals back into the non-ferrous materials, they are removed from the magnets using the magnetic separator. Depending on the type of magnetic separator used, the captured metals removal function is accomplished either manually or automatically (continuously or intermittently) for final disposition and disposal.
It is known that a magnetic separator's ability to capture unwanted metals may be compromised when captured metals are not removed from the magnets in a timely manner. Thus, a magnetic separator that has captured metals on it may thereby have a reduced gauss level. Thus, if any contaminating materials are not timely removed, this condition can often result in the captured metals becoming re-commingled with the non-ferrous materials. This can occur more commonly where manually cleaned magnetic separators are deployed. Thus, due to the needed human interaction to complete the magnet particle removal (or, referred to generally as magnet cleaning), and due to the common difficulties that can be encountered when removing captured metals from powerful permanent magnets, magnetic separators may not be cleaned in a timely manner. This can result in metals becoming re-commingled with the non-ferrous materials, thereby compromising if not fully negating the magnets' ability to perform their designed function. Manually cleaned magnetic separators often offer a more affordable design, but include the limitations as noted above.
In an alternative to the more affordable manually cleaned magnetic separators, another option is to utilize an automatically cleaned magnetic separator. Depending on the application where the magnetic separator is to be used, an automatically cleaned magnetic separator may be a valid alternative. This can be continuously cleaned magnets where the captured metals are immediately removed from the magnets, or an intermittent automatically cleaned magnetic separator where the captured metals are removed on a pre-determined cycle period based on user preference. Either design method is typically more expensive than a manually cleaned magnetic separator and is therefore often not considered as an affordable option.
The continuously cleaned magnetic separators offer some limited design options that are often not practical for many applications where magnetic separators are desired in a process. Additionally, they are typically more expensive and, depending on the severity of metals commingled with the non-ferrous materials being processed, may not justify the extra expense for this style of magnetic separator.
The intermittently cleaned magnetic separators offer more design options as compared to continuous clean magnetic separators. Disadvantages with these designs, however, are at least twofold. Like continuously cleaned magnetic separators, intermittently cleaned magnetic separators are typically more expensive. Additionally, because their automatic metal contaminant removal feature is intermittent, captured metals can be washed off the magnets by oncoming non-ferrous materials flowing past the magnets between cleaning cycles.
In addition, continuously cleaned and intermittently cleaned magnetic separators, having their cleaning cycles initiated using a predetermined cycle, may also therefore result in needless cleaning. That is, for periods during light use or no use, the cleaning cycle may nevertheless be initiated on its intermittent basis, which can cause unnecessary cost and wear.
Thus, there is a need to improve magnetic separators while reducing overall cost of operation.